#include <bits/stdc++.h>

#define MaxN 100005
#define MaxM 500005

std::ifstream InFile("euler.in");
std::ofstream OutFile("euler.out");

template <int NNodes, int NEdges>
struct GraphStruct {
    int N, M;
    struct NodeStruct {
        int Grad;
        struct EdgeStruct {
            int EdgeIndex, Dest;
        };  std::list <EdgeStruct> ADC;
    }   Node[NNodes];

    inline void AddEdge(int x, int y, int EdgeIndex) {
        Node[x].ADC.push_back({EdgeIndex, y});
        Node[y].ADC.push_back({EdgeIndex, x});
    }

    bool Preelim() {
        bool Check = false;
        for (int i=0; i<N; i++)
            Check |= (Node[i+1].Grad&1);
        return !Check;
    }

    bool Used[NEdges];
    std::vector <int> Ciclu;

    int NTravelled;
    void DFS(int Index) {
        for (auto Edge:Node[Index].ADC) {
            if (!Used[Edge.EdgeIndex]) {
                NTravelled++;
                Used[Edge.EdgeIndex] = 1;
                DFS(Edge.Dest);
            }
        }   Ciclu.push_back(Index);
    }

    void FindEulerian() {
        DFS(1);
        if (NTravelled != M) {
            OutFile << "-1\n";
            return;
        }

        for (int i=1; i<Ciclu.size(); ++i)
            OutFile << Ciclu[i] << ' ' ;
    }

};  GraphStruct <MaxN, MaxM> Graph;

void Citire() {
    InFile >> Graph.N >> Graph.M;
    for (int i=0, x, y; i<Graph.M; i++)
        InFile >> x >> y,
        Graph.AddEdge(x, y, i);
}
void Rezolvare() {
    if(Graph.Preelim())
        Graph.FindEulerian();
    else OutFile << "-1\n";
}

int main()
{
    Citire();
    Rezolvare();

    return 0;
}